Polyelectrolyte flocculants in harvesting microalgal biomass for food and feed applications
Polyelectrolyte flocculants in harvesting microalgal biomass for food and feed applications
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DOI：
10.1016/j.algal.2017.03.022
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发表时间：
2017-06
影响因子：
5.1
通讯作者：
Lucie van Haver;S. Nayar
中科院分区：
文献类型：
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作者：
Lucie van Haver;S. Nayar
在工业规模上收获微藻生物质是藻类生物质产业的技术经济瓶颈，因为微藻的细胞尺寸小，培养物中的生物质浓度较低。因此，在收获过程中需要去除大量的水，这使得该过程能源和成本密集，占生物质生产总成本的30%。在商业上采用的各种收集技术中，絮凝法是一种方便、经济的方法。絮凝剂的选择取决于其对多种微藻菌株的有效性，低生物量浓度下的效率，其环境足迹，以及对回收生物量的最终应用的廉价和无毒。在各种絮凝剂中，聚电解质絮凝剂广泛用于各种工业应用，如废水处理和采矿，但也用于有效收获微藻的大量培养。聚电解质絮凝剂是一种分支或线性的聚合物，但沿着它们的链携带离子电荷。它们相应地被分为阳离子、阴离子或非离子聚合物。这些絮凝剂中和细胞表面的电荷，并通过物理或化学力量将颗粒结合在一起。聚电解质絮凝剂的效率取决于所用聚合物的类型、分子量和电荷密度、剂量浓度、介质中的细胞浓度、菌株类型、离子强度和介质的pH值等参数。通过聚电解质絮凝剂大量收集无毒物微藻生物量被认为是最经济可行的技术之一，絮凝剂的成本在1.50至7.50 kg - 1美元之间，并且需要非常低的剂量才能有效收集。本文综述了用于收获微藻的聚电解质絮凝剂在食品和饲料工业中的无毒无残留应用，并评价了各种商用聚电解质絮凝剂及其性能和在高密度培养中收获微藻生物量中的应用。
Harvesting microalgal biomass at industrial scale is a techno-economic bottleneck for the algal biomass industry, compounded by the small cell size of microalgae and dilute biomass concentrations in culture. As a result, large volumes of water need to be removed during harvesting, making the process energy and cost intensive, accounting for up to 30% of the total cost of biomass production. Among the various harvesting techniques adopted commercially, flocculation is convenient and cost effective. The choice of a flocculant depends on its effectiveness on multiple microalgal strains, efficiencies at low biomass concentrations, its environmental footprint, being inexpensive and non-toxic for end application of the recovered biomass. Of the various flocculants, polyelectrolyte flocculants are widely utilised for various industrial applications such as wastewater treatment and mining, but also for effective harvesting of mass cultures of microalgae. Polyelectrolyte flocculants are polymers that are either branched or linear, but carrying ionic charge along their chain. They are accordingly classified as cationic, anionic or non-ionic polymers. These flocculants neutralise surface charges on cells and bind particles together by physical or chemical forces. The efficiency of polyelectrolyte flocculants depend on the type of polymer used, its molecular weight and charge density, dosage concentrations, cell concentration in the medium, type of strain, ionic strength and pH of the medium, and other parameters. Bulk harvesting of toxicant free microalgal biomass by polyelectrolyte flocculants is regarded to be one of the most economically viable techniques, with the cost of flocculants ranging between US$1.50 and 7.50 kg− 1, and requiring very low dosage for effective harvesting. This review focusses on polyelectrolyte flocculants to harvest cultivated microalgae for non-toxic residue free applications of the harvested biomass in the food and the feed industry and evaluates various commercial polyelectrolyte flocculants, their properties and application in harvesting microalgal biomass from high density cultures.